Material handling machine and method

ABSTRACT

The present invention is directed to a machine and method for moving and cutting a continuous web of material. In a preferred embodiment, the machine is a high speed snack bag handling machine operable to move and cut individual filled bags from a continuous web of filled and connected snack bags. Web movement through the machine is achieved by a hand-over-hand movement of a pair of bag grippers which each further include an extendable cutting blade to cut and separate individual bags from the web.

This application claims priority to U.S. Provisional Application Ser.No. 61/641,011 filed May 1, 2012.

BACKGROUND OF THE INVENTION

The present invention relates to material handling. More particularly,the present invention relates to a machine and method for high speedmoving and cutting of a continuous web of material. In a preferredembodiment, the present invention is directed to a high speed snack baghandling machine and method.

Material handling is involved in most aspects of present day industrialmanufacturing and automation. Raw and processed materials used tomanufacture a product require handling as they move through theproduction line. Automated machinery is commonly used to increase themanufacturing efficiency while reducing cost. Such automated machineryis many times custom built according to the type of material beinghandled.

One of the primary duties of material handling equipment is to movein-process manufacturing material from one production process to anotheron the manufacturing floor. Some material handling machinery performs aproduction step on the material and also transports the material to thenext material process station using either integrated material movingcomponents and/or auxiliary robotic machinery, for example.

In high speed manufacturing, material handling machine downtime is to beminimized and preferably avoided if at all possible. It is thereforevery important that the high speed material handling machinery be madeextremely robust so that it is able to withstand the constant vibrationsand forces created by the moving machine components, yet also be able toquickly deal with (preferably with little or no downtime) slightvariations in material sizes and feed rates which are common in such ahigh speed manufacturing environment. Present day technology may offermany machine solutions which would achieve the above objectives,however, very sophisticated machinery usually also means very high cost.There are many manufacturing processes where sophisticated high speedtechnology solutions are not feasible from a cost to manufacturestandpoint. The challenge thus becomes one of designing a machine thatachieves the above performance objectives while at the same time usescost-effective components.

SUMMARY OF THE INVENTION

The present invention provides a material handling machine and methodwhich achieves the above performance objectives and is a relatively lowcost machine solution.

More particularly, the present invention provides a machine and methodfor the high speed handling of a continuous web of material. In apreferred embodiment, the present invention comprises a high speed snackbag handling machine and method which is operable to move an elongatedweb of joined and filled snack bags and perform a cutting operationwhich separates each bag from the web. Although the invention as hereindescribed and shown in the drawing figures is directed at the specificembodiment of snack bag handling, it is understood that the teachings ofthe invention is not limited thereto and may be adapted to othermaterial handling operations.

In the preferred embodiment, the material handling machine includes apair of bag grippers which are operable to grip, move and cut a web ofjoined bags, previously filled with product at an upstream operation,into separated bags which are then prepared for sale (e.g., shipped to awarehouse or retail store). The bag grippers are mounted in laterallyspaced relation to each other along a pair of parallel, spaced guiderails. The grippers are operable to move along their guide rails in asynchronized, “hand-over-hand” fashion where the grippers alternatebetween respective raised and lowered positions such that when onegripper is moving to its raised position, the other is moving to itslowered position.

The bag grippers each include bag gripper arms and respective jaws thatmay be moved between open and closed positions. As one gripper movesfrom the lowered position to the raised position along its guide rail,the gripper jaws thereof are in their open position and not engaging theweb. The web is thus free to travel in between the open gripper jaws.When the gripper is open and being raised, the other gripper jaws areclosed and being lowered (and carrying the captured web along with it).Since the first gripper is open as it is raised, the second gripper,along with the web it is holding, is lowered and passes between thespacing of the open gripper jaws as the grippers pass each other. Thissynchronized and constantly alternating movement of the grippers is whatis referred to herein as gripper-over-gripper or “hand-over-hand”movement of feeding the web through the machine.

A cutting blade is mounted within one of the gripping jaws of eachgripper. When a gripping arm is lowered with the web captured betweenits gripping jaws, the cutting blade is then extended which severs theweb at the gripped location which is between two adjoining bags. Thelower-most bag is thus cut free from the web and may be deposited into ashipping container or delivered to another location as required.

DESCRIPTION OF THE DRAWING FIGURES

The above-mentioned and other features and advantages of this invention,and the manner of attaining them, will become apparent and be betterunderstood by reference to the following description of the invention inconjunction with the accompanying drawing, wherein:

FIG. 1A is a perspective view of a material handling machine accordingto an embodiment of the invention;

FIG. 1B is an enlarged, fragmented, side elevational view of the web ofmaterial seen in FIG. 1A;

FIG. 2A is an enlarged, perspective view of a part of the machine ofFIG. 1 showing the gripper arms in a first position;

FIG. 2B is an enlarged, perspective view of a part of the machine ofFIG. 1 showing the gripper arms in a second position;

FIG. 3A is a perspective view of a gripper arm shown in the openposition;

FIG. 3B is the view of FIG. 3A showing the gripper arm in the closedposition;

FIG. 3C is an enlarged, fragmented view in cross-section of the gripperarm linkage mechanism;

FIG. 3D is a further enlarged, fragmented view in cross-section of theright linkage components seen in FIG. 3C;

FIG. 4 is an enlarged, perspective view of the gripper arm seen in FIG.3A and further including a cam block and cam rollers;

FIG. 5 is an enlarged, perspective view in cross-section of the gripperjaws in the closed condition with the web captured therebetween andready for cutting;

FIG. 6A is a front elevational schematic of an alternate crank arm drivemechanism of the invention;

FIGS. 6B, 6C and 6D are side elevational schematics of an alternatecrank arm drive mechanism of the invention; and

FIGS. 7A and 7B are enlarged detail views of portions of FIGS. 6C and6D, respectively.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring now to the drawing figures, there is seen in FIG. 1A anembodiment of the invention comprising a snack bag handling machine 10designed for high speed separation of individual snack bags 12 a from acontinuous snack bag web 12. While the embodiment shown and describedherein is used for separation of individual snack bags form a continuousweb of snack bags, it will be appreciated that the invention may beadapted to many other material handing operations and is not limited tosnack bag handling. Furthermore, illustrations and references torelative movement direction and orientation of components discussedherein shall not be construed in a limiting sense, it being understoodthat the invention may be used in a variety of orientations as required.

As seen in FIG. 1A, a continuous snack bag web 12 is directed to machine10 from an upstream bag filling operation 14 where a consumable (e.g.,chips) is deposited and sealed into individual, linearly spaced bags 12a along web 12. As seen best in FIG. 1B, each bag 12 a is definedbetween a pair of laterally extending seals 12 b (e.g., by heat sealingfacing panels of material 12 c and 12 d together).

Machine 10 includes a pair of bag grippers 16 and 18 operable to grip,move and cut web 12 into separated bags 12 a which are then prepared forsale (e.g., shipped to a warehouse or retail store). For example, oncecut free of continuous web 12 by one of the grippers 16, 18, theindividual snack bag 12 a may be deposited into a shipping box 20. It isunderstood that the Figures herein show but one possible embodiment of asnack bag boxing operation and the invention is not to be limitedthereby. In this embodiment, a plurality of empty boxes 20 are fed froma supply ramp 22 to a location beneath bag grippers 16, 18 such that thecut bags 12 a may be directed into a box 20. The bags 12 a may bedeposited in any desired array within box 20. The array pattern may becontrolled by moving box 20 and/or the individual bags 12 a (after eachbag 12 a is cut free of the web) into the desired box (or othercontainer) location. Any desired positioning control mechanism may beused including vacuum chucking, pulsed air streams and/or robotic arms,for example. Such control mechanisms may be programmable such that theymay be adjusted to change array patterns and bag sizes as required for aparticular job.

As seen in FIGS. 2A and 2B, bag grippers 16, 18 are mounted in laterallyspaced relation to each other along guide rails 62, 64, respectively.Although not strictly necessary, it is preferred that grippers 16, 18are substantially identical and description of one gripper andassociated components herein is understood to apply equally to the othergripper and associated components. As will be described in detail below,grippers 16, 18 are operable to move along guide rails 62, 64 in asynchronized, “hand-over-hand” fashion. FIG. 2A shows a position wheregripper 16 is at its raised position and gripper 18 is at its loweredposition. In FIG. 2B, gripper 16 is shown in its lowered position andgripper 18 is shown in its raised position. During operation, grippers16 and 18 alternate between their respective raised and loweredpositions such that when one gripper is moving to its raised position,the other is moving to its lowered position. This movement then reverseswith grippers 16 and 18 continuously gripping and feeding web 12 throughmachine 10 as described in more detail below.

FIGS. 3A-3D illustrate various views of gripper 16, it being understoodgripper 18 is preferably substantially identical thereto as mentionedabove. As seen in FIGS. 3A and 3B, gripper 16 includes first and secondgripper arms 16 a, 16 b individually pivotally mounted at pivot pointsP₁ and P₂, respectively, to a bracket 30. Movement about pivot points P₁and P₂ allow gripper arms 16 a and 16 b to alternately move toward andaway from each other. Each gripper arm 16 a, 16 b is inwardly angled atpivot points P₁ and P2 and define upper arm segments 16 a′ and 16 b′ andlower arm segments 16 a″ and 16 b″, respectively. Lower arms segments 16a″ and 16 b″ each include a respective gripper jaw 16 a′″ and 16 b′″which extend substantially perpendicular to their respective gripperarms 16 a, 16 b. Gripper jaws 16 a′″ and 16 b′″ each include arespective jaw surface 19 and 21 (see also FIG. 5) to be discussed inmore detail below.

As stated above, gripper arms 16 a and 16 b move alternately toward andaway from each other about pivot points P₁ and P₂. FIG. 3A illustratesgripper arms 16 a, 16 b in their open (away from each other) positionand FIG. 3B show gripper arms 16 a, 16 b in their closed (toward eachother) position. When moved toward one another to the closed positionseen in FIG. 3B, the facing web jaw surfaces 19 and 21 physicallycapture web 12 therebetween, preferably at the location of a bag closureseam 12 b. When moved away from each other to the open position seen inFIG. 3A, the facing web jaw surfaces 19 and 21 separate and release web12 which then may move separately of gripper 16.

As seen in FIG. 3C, relative movement between gripper arms 16 a and 16 bis assisted via a linkage mechanism 32 which interconnects gripper arms16 a and 16 b at upper arm segments 16 a′ and 16 b′. Mechanism 32includes first and second linkages 34 and 36 pivotally connected to eachother at pivot point P₃. First and second linkages 34 and 36 arepreferably substantially identical to each other and description of oneherein is understood to apply to the other. First and second linkages 34and 36 each include respective first and second linkage components 34 a,34 b and 36 a, 36 b. The second linkage components 34 b and 36 b of eachlinkage are each pivotally connected to upper arm segment 16 a′ and 16b′ via pivot points P₄ and P₅, respectively. First linkage components 34a and 36 a are pivotally connected to each other at pivot point P₃.Pivot points P₁, P₂, P₃, P₄ and P₅ all extend in spaced, parallelrelation to one another.

As seen best in FIG. 3D, first and second linkage components 36 a and 36b may translate relative to one another and are biased toward oneanother via a spring 40. More particularly, in one possible embodiment,second linkage component 36 b includes a hollow projection 36 c whichtelescopes between spaced fingers 36 a′ and 36 a″. Spring 40 is locatedwithin the hollow passage 36 c″ of projection 36 c and includes a firstend 40 a which is located at end wall 36 c′ of projection 36 c. A bolt42 (e.g., a shoulder bolt) passes freely through a washer 43 located atspring end 40 b with bolt head 42 b abutting washer 43. The shank ofbolt 42 passes through spring 40 and exits component 36 b throughaperture 36 c′″ formed in end wall 36 c′. Bolt 42 includes a threadedend 42 a which threads into hole 36 a′″ of linkage component 36 athereby anchoring bolt end 42 a to component 36 a. FIG. 3D shows linkagecomponents 36 a and 36 b slightly spaced from one another which formsgaps such as indicated at G1, G2 and G3 between the first and secondlinkage components 36 a and 36 b. Alignment dowels 44 and 46 may beinserted between respective aligned holes formed in linkage components36 a and 36 b. Either one of the linkage components 36 a, 36 b is notfixed to the dowels such that that component may slide freely on thedowels relative to the other component.

As seen in FIG. 3A, when first and second linkages 34 and 36 are in anangled position relative to one another, first and second gripper arms16 a, 16 b are in their open position, i.e., gripper arm upper segments16 a′ and 16 b′ are moved toward each other and lower arm segments 16 a″and 16 b″ and thus also gripper jaws 16 a′″ and 16 b′″ are moved awayfrom each other.

As seen in FIG. 3B, when first and second linkages 34 and 36 are insubstantially coplanar relationship to one another, first and secondgripper arms 16 a, 16 b are in their closed position, i.e., gripper armupper segments 16 a′ and 16 b′ are moved away from each other and lowerarm segments 16 a″ and 16 b″ and thus also gripper jaws 16 a′″ and 16b′″ are drawn toward one another.

Various mechanisms may be employed to control linkage movement betweenthe coplanar and angled positions described above. In the embodimentshown in the Figures, the linkage control mechanism includes a triggerrod 50 which connects to and extends between linkages 34 and 36 at thelocation of and substantially perpendicular to pivot point P₃. Rod 50includes a head 50 a having a central bore 52 extending therethrough(FIG. 3C). To assist in maintaining proper alignment, the shaft of rod50 may freely extend through a guide block 32 fixed to bracket 30. Asseen best in FIG. 2B, a cylinder and piston type assembly 54 and 56 isassociated with each gripper arm 16 and 18 and may be mounted to abracket upper wall 30 a which is spaced above linkages 36 and 34,respectively. Piston rods 54 a and 56 a extend coaxially with respect tothe trigger rod 50 of the respective linkage 36 and 34 and may movebetween raised and lowered positions. When in the raised position,piston rods 54 a and 56 a are linearly spaced from their respectivetrigger rod 50. When in the lowered position, piston rod lower end 54 b,56 b extends into a respective trigger rod end 52 with a furtherdownward force causing linkages 34 and 36 to pivot about pivot point P₃and move to their coplanar position seen in FIG. 3B.

As seen best in FIG. 2B, piston stops 58 and 60 are mounted onrespective guide rails 62 and 64. When gripper arms 16 and 18 arealternately raised along spaced guide rails 62 and 64, respectively,upper piston end 54 a and 56 a will abut piston stops 58, 60,respectively, with further upward movement of the gripper arms 16, 18causing the piston stops to exert a downward force against the pistonrods which moves them to their lowered positions. As discussed above,when piston rods 54, 56 are lowered, lower piston rod end 54 b, 56 babuts a respective trigger rod 50 and pushes it downward causinglinkages 36 and 34 to pivot about pivot point P₃ and move into theircoplanar relationship. It is noted in FIG. 2B that a verticallyadjustable rod 58′ may be provided to act as the piston stop allowingthe operator to adjust the vertical positioning thereof to adapt to theneeds of a particular job (e.g., when the size and thus spacing betweenthe individual bags 12 a changes the piston stop potion may likewise bechanged to ensure the web is gripped at the appropriate location).

Various drive mechanisms may be used to alternately raise and lowergripper arms 16, 18 along rails 62, 64. For example, linear actuatorswithin guide rails 62 and 64 may be used. Alternatively, a crank armdrive mechanism such as seen in FIGS. 6A-6D may be used. The crank armdrive mechanism may afford a higher degree of robustness as compared tolinear actuators as will be discussed more fully later.

As gripper arm 16 moves from the lowered position to the raised positionalong guide rail 62, gripper jaws 16 a′″ and 16 b′″ are in their openposition (FIG. 3A) and not engaging web 12. Web 12 is thus free totravel between gripper jaws 16 a′″ and 16 b′″. Furthermore, aspreviously mentioned, when gripper 16 is open and being raised, gripper18 is closed and being lowered (and carrying web along with it). Sincegripper 16 is open as it is raised, gripper 18, along with web 12,passes between the spacing of open gripper jaws 16 a′″ and 16 b′″ as thegrippers 16 and 18 pass each other. This synchronized and constantlyalternating movement of the grippers 16 and 18 is what is referred toherein as gripper-over-gripper or “hand-over-hand” movement.

As gripper arm 16 is raised, and upon piston rod end 54 a abutting andpressing further against piston stop 58, piston rod end 54 a is pusheddownwardly against respective trigger rod 50 which is thus also forceddownwardly causing associated linkages 34 and 36 to pivot about pivotpoint P₃ to their coplanar relationship. As linkage components 34, 36are moved to their coplanar relationship, they apply an outward forceagainst their respective gripper upper arm segments 16 a′, 16 b′,thereby causing counter-clockwise (CCW) pivoting of gripper arm 16 aabout pivot point P₁ and clockwise (CW) pivoting of gripper arm 16 babout pivot point P₂ (FIG. 3C). This movement causes gripper jaws 16 a′″and 16 b′″ to move toward one another to the closed position (FIG. 3B).Thus, when moved to the fully raised position, gripper arm lowersegments 16 a″ and 16 b″ move toward one another causing gripper jaws 16a′″ and 16 b′″ to also move toward one another and capture web 12therebetween, preferably at seal seam 12 b as discussed above. Once web12 has been captured between jaws 16 a′″ and 16 b′″, the drive mechanismlowers gripper 16 which takes the captured web 12 along with it. Asdiscussed above, when gripper 16 is being lowered along with capturedweb 12, opposite gripper arm 18 is being raised in the open jaw positionwith gripper 16 passing between the open jaws of arm 18.

With trigger head 50 a seated against block 32, it will be appreciatedthat linkage components 34, 36 will stay in their coplanar relationshipuntil a counter-force is applied at pivot point P₃. Gripper jaws 16 a′″and 16 b′″ thus stay in the closed position during the lowering ofgripper 16 along guide rail 62.

As seen in FIG. 2B, brackets 70 a and 70 b having a respective cam block80 a and 80 b are attached to respective guide rail 62 and 64. Camblocks 80 a and 80 b are laterally spaced from each other a distanceslightly larger than the length “L” of gripper jaws 16 a′″, 16 b′″ andare positioned in the path of gripper arms 16, 18. As seen best in FIG.4, cam block 80 a includes a pair of spaced flanges 81 and 82 whichtaper (widen) gradually toward one another in the downward direction. Assuch, the width of the spacing between the flanges narrows in thedownward direction with the upper spacing width W₁ being slightly largerthan the lower spacing width W₂. Gripper jaws 16 a′″ and 16 b′″ arestill in their closed position and gripping web 12 as they approach camblocks 80 a and 80 b. Gripper jaws 16 a′″ and 16 b′″ further eachinclude cam rollers 84 a, 84 b and 86 a, 86 b, and the lateral spacingof the cam blocks 80 a and 80 b are such that outer cam rollers 84 a and86 a are directed through cam block 80 b and between cam flanges 81 and82 thereof while at the same time inner cam rollers 84 b, 86 b aredirected through cam block 80 a and between flanges 81 and 82 thereof.Since the spacing between the cam flanges 81 and 82 narrows in thedownward direction, the cam rollers are forced even closer together asthey travel therethrough.

Referring to FIG. 5, the gripper jaws 16 a′″ and 16 b′″ are seen in theclosed position with web seam 12 b captured therebetween and prior tothe cam rollers entering the narrowed width W₂ of cam flanges 81 and 82.Web engaging bars 19 and 21 are each spring mounted to respective jaws16 a′″ and 16 b′″. Bars 19 and 21 are biased by springs 90, 92 towardeach other and in a direction away from their respective jaws 16 a′″ and16 b′″. As discussed more fully below, a cutting blade 88 is providedhaving a cutting end 88 a extending through either one of the webengaging bars such as bar 21 with opposite, non-cutting end 88 b fixedto jaw 16 b′″ via bolt 89.

In the closed position seen in FIG. 5, jaws 16 a′″ and 16 b′″ are spaceda distance such that the outwardly biased web engaging bars are grippingweb 12 therebetween. In this condition, a space S₁ is defined betweenjaw 16 a′″ and bar 19 and a space S₂ is defined between jaw 16 b′″ andbar 21. As the cam rollers travel through the narrowed width W₂ betweenthe cam flanges of their respective cam blocks, the cam rollers aresqueezed even closer together. Since the cam rollers are mounted to jaws16 a′″ and 16 b′″, and since bars 19 and 21 are already closed upon web12, this further inward force causes the jaws 16 a′″ and 16 b′″ to movecloser toward one another, pushing against the bias of springs 90 and92, and thereby closing the spaces S₁ and S₂. Since blade 88 is fixed toand moves with jaw 16 b′″, as space S₂ closes, cutting end 88 a projectsoutwardly of web engaging surface 21 and passes through web seal 12 b,thereby cutting and separating the adjoining bags 12 a from each other.Once the cam rollers exit the cam block, the rollers are no longer heldtogether by the cam block and the springs 90 and 92 bias bars 19 and 21away from their respective jaws 16 a′″ and 16 b′″ causing blade cuttingend 88 a to retract within bar 21.

Referring to FIG. 4, trigger rod 50 includes a lower end 50 b. Sincetrigger rod 50 is attached to linkage components 34 and 36, rod 50lowers together with the lowering of the gripper arm 16 along guide rail62. As the cam rollers exit the cam blocks, trigger rod lower end 50 bengages a stop surface 70 a of bracket 70. Further lowering of gripperarm 16 by the drive mechanism causes trigger rod 50 to be pushedupwardly with respect to gripper arm 16. Since trigger rod 50 is fixedlyattached to linkage components 34, 36 at pivot point P₃, upward movementof rod 50 forces linkage components 34, 36 from their coplanarrelationship into their angled relationship. This causes CW movement ofgripper arm 16 a about pivot point P₁ and CCW movement of gripper arm 16b about pivot point P₂ and thus movement of jaws 16 a′″ and 16 b′ awayfrom each other and toward the open position which releases web 12.Since the cutting action has already occurred as described above, thelower-most bag 12 a is released from the web 12 for further downstreamhandling, e.g., deposit into a shipping container such as box 20.

It is noted that during the squeezing together of the cam rollers asthey travel through the narrowed area of the cam blocks, further CWmovement of upper arm segment 16 b′ occurs. Since linkages 32 and 34 areinterconnected and already in their coplanar relationship, the outerlinkage component 36 b is pulled away from linkage component 36 aagainst the bias of spring 40 and translates away from linkage component36 a (FIG. 3D). Thus, once the cam rollers have exited and are no longerconstrained together by the cam blocks, spring 40 urges linkagecomponents 36 a and 36 b back toward each other and thereby closes thegaps G₁-G₃ therebetween. This action assists in the movement of the jaws16 a′″ and 16 b′″ away from each other toward the open position.

FIGS. 6A-6D illustrate another preferred embodiment of the inventionhaving a crank arm drive mechanism and web position sensors. Componentsin FIGS. 6A-6D which are substantially the same as their respectivecomponents in FIGS. 1-5 are indicated by the same reference numberincreased by 100.

As in the embodiment of FIGS. 1-5, grippers 116, 118 are mounted to andoperable to move along guide rails 162, 164 in a synchronized,“hand-over-hand” fashion. FIG. 6A shows gripper 116 in the fully raisedposition while gripper 118 is in the fully lowered position. Gripper 116is mounted to ride along guide rail 162 and is moved by crank arm drivemechanism indicated generally at reference numeral 200. As in theembodiment of FIGS. 1-5, description of the components of crank armmechanism 200 associated with gripper 116 applies to the same respectivecomponents of crank arm mechanism 211 associated with gripper 118.

Crank arm drive mechanism 200 includes a crank rod 210 having a firstend 210 a pivotally connected to a crank arm 212 at pivot point P₆ whichpasses through a selected one of a plurality of linearly spaced throughholes H formed in crank arm 212 (FIG. 6B). As one moves the crank armconnection point from the end 212 b attached to the sprocket gear 214and toward the distal (free) end 212 a of the crank arm 212, thediameter of the crank arm circle C, and thus also the distance of travelof the respective gripper mechanism 116 increases. Thus, when there is aproduct changeover and the length L₃ of the web separable product 12 aincreases, the travel distance necessary to grip the web in theappropriate location may likewise be increased by moving connection ofthe crank arm end 210 a (and thus also pivot point P₆) to one of thethrough holes located closer to crank arm distal end 212 a.

As stated above, crank arm 212 includes an end 212 a which is mounted toand driven by rotating sprocket gear 214 which itself is driven by drivesprocket gear 216 which is in turn driven by a motor (not shown). Alooped belt B₁ interconnects sprocket gears 214 and 216. The drivesprocket associated with each gripper assembly may be operated along acommon drive shaft (not shown).

Crank rod 210 includes a second end 210 b which is pivotally attached togripper mechanism 116 via a stop plate 220 which mounts to grippermechanism 116 through a pivot connection 224 (FIG. 6A). Stop plate 220is mounted to gripper mechanism 116 laterally of grip jaws 116 a′″ and116 b″ at bracket 30, for example. Stop plate 220 is spring loaded andbiased by spring 230 toward crank rod 210. As seen best in FIGS. 7A and7B, a bolt 222 includes a threaded end 222 a which threads into crankrod end 210 b and is thus fixed thereto. Bolt 222 includes a smoothsurfaced shank 222 b which extends from threaded end 222 a through ahole in stop plate 220. Bolt head 222 c is located on the side of stopplate 220 opposite crank rod 210. Spring 230 is mounted to bolt 222 andextends between stop plate 220 and bolt head 222 c. Spring 230 ismounted in a partially compressed condition which applies a biasingforce F₁ against stop plate 220 in a direction away from bolt head 222c. This biases stop plate 220 against crank arm end 210 b and when inthis position, crank rod 210 will travel a first linear stroke distanceD₁ which is equal to the diameter of crank circle C when traveling fromthe upper extent (twelve o'clock position) to the lower extent (6o'clock position) (FIGS. 6B-6D).

Application of an opposing force F₂ against stop plate 210 which isgreater than the biasing force of the spring 230 pushes stop plate 220away from crank rod end 210 b and further compresses spring 230 betweenstop plate 220 and bolt head 222 c. This position is seen in FIG. 7Bwherein crank rod 210 has been linearly separated from stop plate 220 bya distance D₂. This effectively shortens the stroke crank rod 210 by adistance D₂ (see FIGS. 6B and 7B) and thus also shortens the strokelength of gripper mechanism 116 (the total distance of stokeD_(T)=D₁−D₂) as described more fully below.

An eccentric stop 240 is mounted to sprocket 260 which is rotated bysprocket gear 262 via a motor (not shown) and looped belt B₂ (FIG. 6B).The sprocket gears associated with an associated gripper arm may bedriven along a common drive shaft. Eccentric stop 240 is rotated oncommand via signals received from a sensor 280 (FIG. 6A) positioned todetect the position of an approaching bag seam 112 b (or otherappropriate detectable element on web 112) relative to the location ofthe grip location (where the gripper jaws of the upper-most grippermechanism are about to be triggered closed on the web in the mannerdescribed above). If the position of the seam has varied from thelocation where the gripper jaws will be triggered to close, the sensorsends a command to the eccentric stop to make it rotate to a rotationalposition which will change the stroke length by an amount compensatingfor the variance.

More particularly, as seen in FIG. 6A, eccentric stop 240 is positionedat a location slightly above the location of gripper jaws 116 a′″ and116 b′″when at the upper extent of travel. When the smallest radius ofeccentric stop 240 is at the 6 o'clock position, stop plate 220 willabut eccentric stop 240 without application of force F₂ which meansplate 220 is biased against crank rod end 210 b and the travel distanceof gripper 116 will thus be D₁. Should upstream sensor 280 detect thatthe position of a bag seam 112 b has varied from where it should be(i.e., at a location which, when speed of web travel is factored in, thesensor calculates it will arrive at the location of the gripper jaws atthe exact moment they are triggered closed in the manner describedabove), a signal is sent from sensor 280 to rotate eccentric stop 240such that it presents the appropriate radius thereof at the 6 o'clockposition. For example, a larger eccentric radius at the 6 o'clockposition means the stop plate 220 will abut the eccentric stop prior tocrank rod 210 reaching its upper extent of travel such that its stroke(and gripper 116 to which it is attached) is adjusted. This adjusteddistance of stroke travel may be of an amount anywhere between thesmallest radius R_(S) and largest radius R_(L) of eccentric stop 240(where R_(L)−R_(S)=D₂ where D₂ is the maximum amount of distance thecrank arm stroke may be shortened. Once the stroke has been shortened,it may of course be again lengthened on command of sensor 280 byrotating the eccentric toward R_(S). Depending on whether the varianceis a foreshortening or a lengthening, the sensor will trigger theeccentric to rotate in the appropriate direction to present either alarger radius or smaller radius to the rising stop plate in order tocompensate for the variance. In a preferred embodiment, the signalcausing the eccentric stop to rotate to compensate for a variance may beat any desired point between the 6 o'clock and 12 o'clock positions ofthe crank arm revolution.

It is noted that the crank arms controlling the respective gripper arms116 and 118 are 180° out of phase. As such, the weight of one gripperassembly is counter-balance by the weight of the other gripper assembly.This balances the machine which decreases the amount of energy requiredto drive the machine. Further, it will be appreciated that two productbags 12 a are processed (cut and transferred to processing location suchas box 20) per input revolution.

It will thus be realized that sensor 280 and eccentric stop 240 may beused to ensure the desired web grip location (e.g., at a seam 112 b) islocated at the gripper jaws when they are triggered closed. As such,slight variances, which inevitably creep into and cause the desired webgrip location to be offset from the gripper jaws when triggered closed,may be compensated for without machine downtime or human intervention.

While this method and apparatus has been shown and described withreference to certain preferred embodiments thereof, it will beunderstood by those skilled in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the invention as described.

What is claimed is:
 1. A high speed material handling machinecomprising: a) first and second parallel, spaced guide rails; b) firstand second gripper assemblies mounted to a respective guide rail inlaterally spaced relation with one another, each gripper assemblyincluding: i) first and second gripper arms pivotally mounted to abracket between an open and a closed position, each gripper armincluding an upper arm segment and lower arm segment with the lower armsegment having a gripper jaw which extends substantially perpendicularto its respective gripper arm and includes a gripper jaw surface adaptedto capture material therebetween when in the closed position; ii) alinkage mechanism interconnected to the upper arm segments through firstand second linkages which are pivotally connected to each other whereineach linkage includes respective first and second linkage componentsadapted to translate relative to one another and are biased toward oneanother by a biasing member; wherein the first and second linkages arein an angled position when the gripper arms are in the open position andare substantially coplanar to one another when the gripper arms are inthe closed position; iii) a linkage control mechanism to controlmovement of the linkage mechanism between the angled and substantiallycoplanar positions, the linkage control mechanism including: a) atrigger rod connected to and extending between the linkages, the triggerrod having a head with a central bore; b) a cylinder and piston assemblyincluding a piston rod extending coaxially with the trigger rod whereinthe piston rod is linearly spaced from the trigger rod when in anextended position and wherein the piston rod impacts the central bore ofthe trigger rod when in the compressed position thereby engaging thetrigger rod to cause the linkages to pivot to the coplanar position; andc) a drive mechanism to alternately raise and lower the gripper armassemblies in a synchronized fashion wherein the first and secondgripper assemblies alternate between a respective raised and loweredposition, wherein as one of the gripper assemblies moves from thelowered position to the raised position along its respective guide rail,the gripper jaws thereof are in the open position and not engaging thematerial such that the material is free to travel in between the opengripper jaws, and wherein when the one of the gripper assemblies is openand being raised, the gripper jaws of the other of the gripperassemblies are closed and being lowered thereby carrying the capturedmaterial such that it passes between the spacing of the open gripperjaws as the gripper assemblies pass each other.
 2. The high speedmaterial handling machine of claim 1 wherein at least one gripperassembly has gripper jaws equipped with a cutter.
 3. The high speedmaterial handling machine of claim 2 wherein the gripper assemblybracket of the gripper assembly carrying the gripper jaws equipped withthe cutter includes a cam block having a pair of spaced flanges whichtaper gradually toward one another such that cam rollers situated on thegripper jaws engage the cam block between the spaced flanges therebycausing the gripper jaws to be increasingly directed toward one anothersuch that the material captured between the gripper jaws is cut with thecutter.
 4. The high speed material handling machine of claim 1 furthercomprising a piston stop mounted onto each respective rail wherein eachrespective piston rod impacts upon its respective piston stop therebycausing the piston rod to engage the trigger rod to pivot the linkagesto the coplanar position.
 5. The high speed material handling machine ofclaim 4 wherein the piston stop is adjustable.
 6. The high speedmaterial handling machine of claim 1 wherein the drive mechanism is alinear actuator.
 7. The high speed material handling machine of claim 1wherein the drive mechanism is a cam arm drive mechanism, the cam armdrive mechanism comprising a crank rod having a first end and a secondend, wherein the first end is pivotally connected to a crank arm at apivot point which passes through a selected one of a plurality oflinearly spaced through holes formed in the crank arm and wherein thesecond end is pivotally mounted to a respective gripper assembly via astop plate; and wherein the crank arm has a first end and a second endwherein the first end is attached to a rotating sprocket gear such thatthe pivot point is located between the rotating sprocket gear and thesecond end of the crank arm, and wherein the rotating sprocket gear isdriven by a drive sprocket gear through a connecting looped belt.
 8. Thehigh speed material handling machine of claim 7 wherein the cam armdrive mechanism further comprises an eccentric stop adapted to receivecommand signals from a sensor so as to rotate the eccentric stop therebyadjusting a stroke length of said cam arm drive mechanism.
 9. The highspeed material handling machine of claim 7 wherein the crank arms are180° out of phase.